But the bullet continues to accelerate even as pressure behind it diminishes. Pressure drops off fast, too, losing 90 percent of its vigor in the next 18 inches of barrel. Bullet Ballistics: Peak PressureĪ few things to note: First, peak pressure comes when the bullet has moved only about 3 inches, even with the slow-burning fuels appropriate for a. Receivers easily endure 60,000-psi – and more. Surgeon rifles start as solid steel billets.
ITHACA MODEL 49 HIGH VELOCITY AMMO MANUAL
The following bullet ballistics chart shows what happens (data adapted from a pressure/time curve in the excellent text Any Shot You Want, a loading manual by Art Alphin’s A-Square company). 300 Weatherby Magnum exits the muzzle of a 26-inch barrel about 1 1/4 milliseconds after it starts to move. The bullet is on its way.Ī 180-grain bullet from a. Two to three milliseconds after the striker hits the primer, pressure has dropped to zero. The area under this pressure/time curve translates to bullet velocity. The faster the powder, the steeper the curve on both sides.
This decline is relatively gradual as the bullet moves forward, increasing the bore volume behind it. On a bullet ballistics graph, you’ll see a pressure peak after a short horizontal line showing the delay between primer detonation and powder ignition.Īfter that peak, which typically happens within a millisecond (1/1,000 second) after the powder starts to burn, the pressure curve arcs back down.
When a primer spits fire into the powder charge and burning commences, gases form, increasing pressure inside the case and (because pressure produces heat), accelerating the burn. With 55,000 psi under your eye, stout lockup, flawless steel and perfect headspace matter.
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